Examinando por Materia "B3LYP functional"

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    Electronic and Topological Analysis for New Phases of Chromium Nitride
    (WILEY-V C H VERLAG GMBH, 2018-01-01) Marin-Suarez, Marco; Alzate-Vargas, Leidy L.; David, Jorge; Arroyave-Franco, Mauricio; Velez, Mario E.; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)
    Chromium nitride (CrN) in its NaCl-type phase has been widely studied through density functional theory (DFT) in order to analyze its electronic properties. By the means of DFT with the Becke's three parameter Lee-Yang-Parr (B3LYP) hybrid functional, the same stoichiometry is studied in two unreported hypothetical phases in addition to the nonsynthesized and previously reported zinc-blende-type phase. The cohesive energy of every structure is calculated, and the analysis of this quantity indicated that all crystals are stable and that there is an unreported phase more stable than the synthesized one. The calculated electronic dispersion relation and density of electronic states allowed for the determination that these three phases have a conducting behavior. The symmetry of some bands is determined as a result of the crystal field splitting for chromium d states. The topology of the electron density was studied in order to determine its properties at bond critical points (BCPs). The form of the Laplacian of the density and its gradient trajectories allowed to locate ring critical points in these structures. From these calculations, it is concluded that all three phases are ionic crystals. The synthesized NaCl-type phase is studied in order to compare and confirm the results. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Stratifying the potential local transmission of Zika in municipalities of Antioquia, Colombia
    (Blackwell Publishing Ltd, 2017-10-01) Ospina J.; Hincapie-Palacio D.; Ochoa J.; Molina A.; Rúa G.; Pájaro D.; Arrubla M.; Almanza R.; Paredes M.; Mubayi A.; Ospina J.; Hincapie-Palacio D.; Ochoa J.; Molina A.; Rúa G.; Pájaro D.; Arrubla M.; Almanza R.; Paredes M.; Mubayi A.; Universidad EAFIT. Departamento de Ciencias; Lógica y Computación
    OBJECTIVE To stratify and understand the potential transmission processes of Zika virus in Colombia, in order to effectively address the efforts on surveillance and disease control. METHODS We compare R-0 of Zika for municipalities based on data from the regional surveillance system of Antioquia, Colombia. The basic reproduction number (R-0) and its 95% confidence intervals were estimated from an SIR model with implicit vector dynamics, in terms of recovered individuals in each time unit, using an approximate solution. These parameters were estimated fitting the solution of the model to the daily cumulative frequency of each Zika case according to symptoms onset date relative to the index case reported to the local surveillance system. RESULTS R-0 was estimated for 20 municipalities with a median of 30 000 inhabitants, all located less than 2200 m above sea level. The reported cases ranged from 17 to 347 between these municipalities within 4 months (January to April of 2016). The results suggest that 15 municipalities had a high transmission potential (R-0 > 1), whereas in five municipality transmissions were potentially not sustaining (R-0 < 1), although the upper bound of the confidence interval of the R-0 for 3 of these 5 was greater than one, indicating the possibility of an outbreak later on. CONCLUSION The study identified high-risk municipalities (R-0 > 1) and provide a technique to optimise surveillance and control of Zika. Health authorities should promote the collection, analysis, modelling and sharing of anonymous data onto individual cases to estimate R-0.